New analytical techniques were developed and used in enzymatic research and in clinical investigations of lipidoses. Gaucher's disease is a lipidosis caused by a deficiency of the lysosomal enzyme, glucocerebrosidase. Significant changes occur in the bone marrow of patients with this disease. In order to understand the biochemical basis of these changes, a study of the lipid components of normal and Gaucher's bone marrow was continued. A pronounced drop in the triglyceride level of Gaucher marrow 51 +/- 53 mg/g wet weight) relative to normal controls (278 +/- 70 mg/g wet weight) is by far the greatest change of all lipids on a weight basis. This decrease greatly overshadows the increase in glucocerebroside, and leads to an overall decrease in marrow lipids in Gaucher's disease. This explains the decrease in fat fraction that has been previously seen in magnetic resonance imaging studies of bone marrow in patients with Gaucher's disease. it is probable that these changes are due to the displacement of marrow adipocytes by infiltrating Gaucher macrophages.